Protecting Horticultural Commodities

Ethylene production

After harvest, most fruits and vegetables produce ethylene gas as a natural by-product. If properly managed, ethylene can be used to control the ripening of produce. However, unmanaged exposure to ethylene may harm commodities and cause unwanted ripening, senescence and other physiological damage.

Products have varying ethylene production rates (see the table below). They also vary in their sensitivity to ethylene. Ethylene sensitivity depends on the commodity and on the temperature, oxygen and carbon dioxide levels, exposure time and ethylene concentrations. It is important to note that some commodities are sensitive to ethylene concentrations as low as 0.1ppm (parts per million) when exposed to ethylene for long periods of time.

Sample rates of ethylene production

Reducing ethylene: temperature and atmosphere

Ethylene production is directly related to temperature. Typically, the higher the temperature, the greater the rate of ethylene production and the higher the respiration rate. That is why it is crucial to be aware of the temperature tolerance for each product where ethylene production is a problem. Fresh-air exchange* can limit the build-up of ethylene in a load. Modified atmosphere* (MA) and controlled atmosphere* (CA) conditions can also help reduce ethylene production and activity.

* Refer to the "Leading the way with state-of-the-art technology & equipment" section for more details.

Ethylene production rates increase with greater maturity, physical injury, disease and increased water stress. Ethylene also arises from other sources in the environment, such as aircraft, automobile and truck exhaust, smoke from cigarettes and gases from rubber materials exposed to heat or ultraviolet light. To prevent damage, always protect agricultural products from these sources of ethylene.

Evaporation and water loss

Loss of water from horticultural crops after harvest is an important factor in a product life cycle and a major cause of deterioration. Perishables that have lost water become dehydrated, weigh less and are of poorer quality in the marketplace.

All fruit and vegetable commodities tend to give off moisture in widely varying amounts. Some products are affected by higher water loss as compared to others. In general, leafy vegetables tend to lose water at a more rapid rate than fruit, which has less surface area to expose. Plants that have been bruised or cut will lose water faster than those that are undamaged.

As such, maintaining proper temperature and relative humidity - the ratio of the total water vapor content of the air to its total capacity at a given temperature - helps keep water loss to a minimum. APL recommends high humidity 85%-95% and low temperature - the lowest safe temperature for the particular product - for most fruits and vegetables.

Pre-cooling and water loss

Rapid pre-cooling of the product is also important because water evaporates more rapidly at higher temperatures.

Packaging and water loss

Appropriate packaging can keep water loss to a minimum. However, do keep in mind that packaging can also reduce the rate of cooling by restricting air movement around the perishables.

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